1. Field of the Invention
The present invention relates to method and apparatus for detecting or examining the state of micro-holes formed, and more particularly, it relates to a method and apparatus for detecting or examining the state of a plurality of micro-holes formed on the outer circumference of a rod-like object such as a cigarette.
2. Description of the Related Art
Filtered cigarettes give the smoker a lighter taste. Further, some filtered cigarettes have a plurality of micro-holes formed on the outer circumference of each of them so as to dilute smoke flowing through them and decrease the temperature of this smoke. In this type of filtered cigarette, the smoke inhaled into the mouth of the smoker, flows through the cigarette from the tobacco side to the filter side of the cigarette, and is diluted by air sucked into the cigarette through the micro-holes formed on its filter section and through its paper roll.
However, the amount of air sucked into the cigarette through the micro-holes and paper roll must be kept constant in order to provide an enjoyable taste to the smoker. It must be therefore be checked whether or not the amount of air sucked into the cigarette is kept constant. In order to meet this purpose, methods of detecting the amount of air sucked or the dilution of the cigarette have been provided and apparatus for carrying out these methods have also been developed.
Japanese Patent Disclosure Sho 57-194339 discloses one of these methods of detecting the amount of air sucked into the cigarette through the microholes formed on its outer circumference and through its paper roll. In the case of this method, compressed air having a predetermined pressure is supplied into the cigarette from the tobacco side thereof, pressure run out of the cigarette from the filter side thereof is detected by a pressure transducer and the amount or degree of air sucked into the cigarette is calculated on the basis of the pressure detected on the filter side of the cigarette and at the predetermined pressure supplied into the tobacco side the cigarette.
The equation relating to the dilution of the cigarette is generally expressed as follows and a dilution value (D) is calculated using this equation. EQU D=B/A.times.100=(A-C)A/.times.100(%)
where D represents the dilution value of the cigarette, A the amount of air inhaled into the mouth of the smoker, B the amount of air sucked into the cigarette through the outer circumference thereof, and C the amount of smoke inhaled into the mount of the smoker, flowing through the cigarette from the tobacco side thereof.
When this equation is replaced by an equivalent circuit, the following equation is created: EQU D=(P1-P2)/P1.times.100%
wherein P1 represents the predetermined pressure supplied into the cigarette and P2 the pressure run out of the cigarette and detected.
In the case of the conventional methods of detecting the amount of air supplied into the cigarette, the pressure run out of the cigarette is detected only on the filter side of the cigarette. The pressure supplied into the cigarette is not detected on the tobacco side of the cigarette but the dilution value (D) is detected because the predetermined pressure is usually applied into the cigarette from the tabacco side thereof. When a time period long enough to keep the pressure in the cigarette at the value of that pressure which is supplied into the cigarette from the tobacco side exists, a sufficiently accurate dilution value (D) of the cigarette can be detected. In the case where this dilution measuring method is employed in the manufacturing process of carrying the cigarettes at relatively low speed, the dilution values can be relatively accurately measured.
However, the cigarettes are now carried at high speed in the manufacturing process so as to enhance productivity. This results in the pressure run out of the cigarette being detected before the pressure in the cigarette reaches the value of that pressure which is supplied into the cigarette, thereby making it impossible for the dilution to be accurately detected. Namely, when the speed at which the cigarettes whose dilution is to be detected are carried is higher than the speed at which the detecting pressure reaches the filter end of the cigarette through the tabacco end thereof, the pressure run out of the cigarette cannot be detected with the same accuracy as in the case where the cigarettes are carried at low speed, because the cigarette is shifted out before the detecting pressure reaches the filter end of the cigarette from the tobacco end thereof. Detection accuracy therefore is very low.
In the case of the conventional detector apparatuses, micropressure is obtained by increasing the pressure through an orifice and calculating the flow rate of this increased pressure, but pressure detection after this pressure increasing process causes its accuracy to be very low also.